Some pilots when furloughed after years of exemplary service and thousands of hours in the RHS have failed to even be invited to interview with prospective new employers due to their lack of jet PIC time. In an unstable job market it's surprisingly easy to find yourself outside looking in whilst clutching a very respectable logbook which still unfortunately fails to pass muster.
As 411A states, the LHS can be the holy grail of employment - but the cost to QOL can be considerable. One size doesn't fit all and the compromises made will be to individual choice.
As for the seniority thing: pilots are much of a muchness, with a total absence of seniority how would promotions be assigned?
Perhaps those prepared to fly when ill, or in less than airworthy aircraft, or with slim fuel margins, or being willing to abrogate authority but retain ultimate responsibility would float to the top for management's nod of approval and clearance to further ascend the greasy pole of career ambition.